The nation's most powerful voice against same-sex marriage is entering the battleground in Wisconsin, where voters in November will decide the fate of a proposed constitutional ban on gay marriage.

Focus on the Family, the conservative Colorado Springs-based group led by James Dobson, filed papers with the state Elections Board last week to create a referendum committee. The group has spent more than $1 million passing anti-gay marriage legislation in other states and the stakes here are high: Wisconsin has been pegged by analysts as perhaps the first state that stands a chance of defeating a same-sex marriage ban.